Nai are very similar to humans. The few differences they have are an extra pair of arm, an bald, elongated head and a flattened nose.
The nali religion is similar to Budhism. It frowns on violence and has it's own god. Few actual beliefs are known outside Na Pali. What is known is that the nali believe the skaarj to be demons sent down by angry gods because of something they done. They believed that one day, a chosen one would free them from their "demonic" masters and bring their world peace. Two of their few known gods is Chizra, the water god and Vandora, the goddess of lightning.
Before the events of the first game (Unreal), the nali were enslaved by the skaarj. The skaarj forced the nali to mine tarydium crystals from the Rrajigar Mines. They weren't allowed to leave and so the skaarj kept them under guard at all times so they wouldn't teleport. The nali would pray for the chosen one to appear and save them. When the human prison ship Vortex Rikers crashed on Na Pali, they thought their prayers had been answered by Prisoner 849 AKA Gina. She escaped the planet, killing the skaarj queen and freeing the nali in Rrajigar in the process, but was sent back by the captain of the battle cruiser UMS Bodega Bay to find a lost ship, the UMS Prometheus. As the prisoner went back across the planet to find the ship and then, when she learnt of the Bodega Bay's betrayal, to escape again, she freed more colonies, but not all. She killed the skaarj warlord in charge of the clan on Na Pali, leaving it completely leaderless, but otherwise, the nali are still waiting for divine intervention.